Photo-patterned carbon electronics

ABSTRACT

A system is provided for the manufacture of carbon based electrical components including, an ultraviolet light source; a substrate receiving unit whereby a substrate bearing a first layer of carbon based semiconductor is received and disposed beneath the ultraviolet light source; a mask disposed between the ultraviolet light source and the carbon based semiconductor layer; a doping agent precursor source; and environmental chemical controls, configured such that light from the ultraviolet light source irradiates a doping agent precursor and the first carbon layer.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/497,752 filed Jul. 6, 2009 and U.S. patent application Ser. No.11/404,435, filed Apr. 14, 2006.

FIELD OF THE INVENTION

The invention relates to the manufacture of carbon based semiconductorcomponents, and more particularly, to photo patterned carbon electricalcomponents and a method for the manufacture thereof.

BACKGROUND OF THE INVENTION

Known methods of forming semiconductor electronic components requiresuccessive masking and photo-etching steps through which horizontalstructures and doped layers of semi-conductors are built up from asubstrate. The components thus produced are typically comprised ofsilicon, gallium, indium, and other p-bock semi-metallic elements towhich dopants are introduced to effect changes in the electronicconfiguration of the semiconductor crystal. In use, known semiconductorsgenerate heat, and lose effectiveness when in high heat environments.Consequently, cooling systems, such as heat sinks and fans are typicallybe employed to prevent heat damage to the electronic component, and inhigh speed and high voltage applications, special selections ofmaterials are made. Known materials, even those specifically selectedfor their thermal properties, perform suboptimally in high temperatureenvironments.

Recently, the unique electrical and thermal properties of variousallotropes of carbon, such as carbon nanotubes and diamond-like carbon,and other organic compounds like graphene have been the object of muchstudy. The creation of effective electrical components that incorporatethe useful properties of carbon allotropes and molecules intosemiconductor electronics, such as transistors have been theorized.While the properties of these carbon molecules make them the subject ofmuch interest as potential semiconductors, suitable doping techniqueshave proved illusive.

What is needed, therefore, are techniques for producing cost effectivecarbon based semiconductor electrical components.

SUMMARY OF THE INVENTION

One embodiment of the present invention provides a system for themanufacture of carbon based electrical components, the systemcomprising: a ultraviolet light source; a substrate receiving unitwhereby a substrate bearing a first layer of carbon based semiconductoris received and disposed beneath the ultraviolet light source; a maskdisposed between the ultraviolet light source and the first layer ofcarbon based semiconductor; and a doping agent precursor source; andenvironmental chemical controls, configured such that light from theultraviolet light source irradiates a doping agent precursor and thefirst carbon layer.

Another embodiment of the present invention provides such a systemwherein the ultraviolet light source emits light in a spectrum selectedfrom the group of spectra consisting of Deep Ultraviolet Light andExtreme Ultraviolet Light.

A further embodiment of the present invention provides such a systemwherein the ultraviolet light source comprises a stepper laser.

Yet another embodiment of the present invention provides such a systemfurther comprising an optical component disposed between the mask andthe first layer of carbon based semiconductor.

A yet further embodiment of the present invention provides such a systemwherein the optical component comprises at least one optical componentselected from the group of optical components consisting of a lenses,arrays of lenses, diffraction gratings, optical wave guides, andmirrors.

Still another embodiment of the present invention provides such asystem, wherein the optical component is resistant to chemical attack.

A still further embodiment of the present invention provides such asystem further comprising a docked coating tool communicating with thesubstrate receiving unit, whereby the substrate wafer is received andcoated with the first carbon layer.

Even another embodiment of the present invention provides such a systemwherein the docked coating tool is configured to provide at least asecond carbon layer and reintroduce the substrate layer and the firstcarbon layer, together with the second carbon layer to the receivingunit.

An even further embodiment of the present invention provides such asystem wherein the doping agent precursor source is a gas supply.

Still yet another embodiment of the present invention provides such asystem wherein the doping agent precursor source is a condensed phasefluid configured to apply the doping agent precursor to the first carbonlayer by spinning.

A still even further embodiment of the present invention provides such asystem wherein the doping agent precursor is selected from the group ofdoping agent precursors consisting of COF₂, CF₂Cl₂, CF₂Br₂, CF₃Br, CF₃I,CF₃NO, CO(CF₃), Cesium, Potassium, Hydrogen, Oxygen, Fluorine dimer,Chlorine dimer, and Iodine dimer.

Even yet another embodiment of the present invention provides such asystem wherein the environmental chemistry controls are configured tosubstantially exclude non-selected doping agent precursors.

An even yet further embodiment of the present invention provides such asystem wherein the system comprises components resistant to chemicalattack.

One embodiment of the present application provides a method for theproduction of carbon based electrical components, that methodcomprising: providing a wafer substrate; depositing upon the wafersubstrate a first layer of carbon based semiconductor; introducing thefirst layer of carbon based semiconductor to a first doping agentprecursor; irradiating the first doping agent precursor and the firstlayer of carbon based semiconductor with light having a wavelength inthe ultraviolet spectrum thereby selectively doping areas of the firstlayer of carbon based semiconductor.

Another embodiment of the present invention provides such a methodwherein the method further comprises: depositing a second layer ofcarbon based semiconductor upon the first layer of carbon basedsemiconductor; introducing the second layer of carbon basedsemiconductor to the first doping agent precursor; and irradiating thefirst doping agent precursor and the second layer of carbon basedsemiconductor thereby selectively doping areas of the second layer ofcarbon based semiconductor.

A further embodiment of the present invention provides such a methodwherein the doping agent precursor is selected from the group of dopingprecursors consisting of COF₂, CF₂Cl₂, CF₂Br₂, CF₃Br, CF₃I, CF₃NO,CO(CF₃), Cesium, Potassium, Hydrogen, Oxygen, Fluorine dimer, Chlorinedimer, and Iodine dimer.

Yet another embodiment of the present invention provides such a methodfurther comprising the steps of: introducing the first layer of carbonbased semiconductor to a second doping agent precursor; irradiating thesecond doping agent precursor and the first layer of carbon basedsemiconductor with a laser thereby selectively doping areas of the firstlayer of carbon based semiconductor.

A yet further embodiment of the present invention provides such a methodwherein the first carbon layer is comprised of a carbon layer having astructure selected from the group of structures consisting of graphene,diamond-like carbon, single walled nanotube mats; sp2 bonded carbonmolecules, and carbon molecules having both sp2 and sp3 bonded carboncenters.

Still another embodiment of the present invention provides such a methodfurther comprising depositing and irradiating a plurality of carbonlayers.

A still further embodiment of the present invention provides such amethod further comprising: selecting a photolithography mask having adesired doping pattern; and disposing the photolithography mask betweenthe light and the first layer.

One embodiment of the present invention provides a carbon basedelectrical component, that carbon based electrical component comprising:a three dimensional carbon based electrical circuit comprising aplurality of layers of carbon material; at least one section of eachlayer in the plurality of layers being doped in at least one layerdoping pattern; the at least one layer doping pattern of each the layerbeing aligned to the at least one layer doping pattern in an adjacentlayer of the plurality of layers so as to produce a desired verticalcircuit.

The features and advantages described herein are not all-inclusive and,in particular, many additional features and advantages will be apparentto one of ordinary skill in the art in view of the drawings,specification, and claims. Moreover, it should be noted that thelanguage used in the specification has been principally selected forreadability and instructional purposes, and not to limit the scope ofthe inventive subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a method for processing of acarbon based semiconductor configured in accordance with one embodimentof the present invention.

FIG. 2 is a block diagram illustrating an apparatus for processing of acarbon based semiconductor configured in accordance with one embodimentof the present invention.

FIG. 3A is a block diagram illustrating a deposition step in a methodfor processing of a carbon based semiconductor configured in accordancewith one embodiment of the present invention.

FIG. 3B is a block diagram illustrating a photo excitation step in amethod for processing of a carbon based semiconductor configured inaccordance with one embodiment of the present invention.

FIG. 3C is a block diagram illustrating a detail of a deposition step ina method for processing of a carbon based semiconductor configured inaccordance with one embodiment of the present invention.

FIG. 3D is a block diagram illustrating a subsequent deposition andexcitation step in a method for processing of a carbon basedsemiconductor configured in accordance with one embodiment of thepresent invention.

FIG. 3E is an elevation view of a multilayer carbon based semiconductorconfigured in accordance with one embodiment of the present invention.

FIG. 3F is an elevation view of a three dimensional multilayer carbonbased semiconductor circuit configured in accordance with one embodimentof the present invention.

FIG. 4 is an elevation view of a carbon based semiconductor coated in adense phase doping agent precursor configured in accordance with oneembodiment of the present invention.

FIG. 5 is an elevation view of a three dimensional multilayer carbonbased semiconductor circuit being successively built up by thedeposition and processing of carbon based layers configured inaccordance with one embodiment of the present invention.

DETAILED DESCRIPTION

One embodiment of the present invention provides a method for theproduction of semiconductor component using deep ultraviolet (DUV) andextreme ultraviolet (EUV) radiation to induce the adsorption of dopingagents into a carbon semiconductor.

In one such embodiment, photolithographic masking may be employed toexpose patterns on a region of a workpiece to radiation in the UVradiation.

Diamond Like Carbon (DLC) thin films and Single wall nanotubes (SWNTs)have electrical and chemical properties making them especially suitablefor semi conductor structures. In their un-doped state, DLCs areinsulators, while SWNTs have a slight N-type bias. Diamond-like Carbonfilms have a high hardness, are chemically inert, and exhibit a highdegree of thermal conductivity.

In one embodiment SWNTs may be doped by the introduction of halide oralkali metals as electron acceptors or donators, respectively. As uptakeof dopant by both DLC thin films and SWNTs can be controlled by exposureto ultraviolet light, ultraviolet light may be used to effect a changein the electrical character of the structure.

ArF or KrF laser radiation is used, in some embodiments to dissociatehalide molecules producing halogen radicals, while other embodimentsutilize such radiation to increase the energy of the moleculesfacilitating bonding with the carbon based layers. Compounds used asdoping precursors include, but are not limited to, COF₂, CF₂Cl₂, CF₂Br₂,CF₃Br, CF₃I, CF₃NO, and CO(CF₃). Gas phase Group 1 metals may likewisebe used, such as Cesium or Potassium.

In one embodiment, dissociation of these molecules generates highlyreactive radicals. DLC films and SWNTs are exposed to the highlyreactive radicals thus produced. The reactive radicals bond with the DLCfilms and SWNTs.

In some embodiments, inorganic gas sources may be provided, introducingsimple gas phase inorganic molecules, including but not limited tohydrogen dimer, oxygen dimer. It has been found that the introduction ofsuch simple inorganic compounds into the gas permits greater control ofthe material properties of the resulting semiconductor.

Chemisorption of Hydrogen or Oxygen can give rise to insulativeproperties. While in some applications this may be valuable, in oneembodiment of the present invention, the doping process is conducted ina closed environment from which Hydrogen and Oxygen are substantiallyexcluded. As these atmospheric gases are light dissociative or excitableand reactive, their presence between the light source's lens and thewafer would lead to unwanted modification of the electrical propertiesof the wafer.

As illustrated in FIGS. 1 and 2 a block diagram illustrating a systemconfigured according to one embodiment of the present invention. In thissystem a docked coater 12 received a substrate wafer 30, the substratewafer 30 is coated with a layer of carbon or carbon based semiconductor32. The carbon layer 32 is introduced to a processing unit, which in oneembodiment is a DUV/EUV stepper scanner. The stepper scanner may includea Deep Ultraviolet or Extreme Ultraviolet light source 34 is equippedwith the capacity to control the chemistry of the process environment.Within the system, a wafer 30 and subsequent carbon layers 32 may becoated by the coater 12 and irradiated by stepper 34 a number ofiterations until a completed electrical component is produced withoutcleaning or etching of the work piece. The completed wafer 10 is thenexpelled from the docked coater 12.

As illustrated in FIG. 2 a mask, such as a photo lithographic mask 58,is disposed in the path of an ultraviolet light source. Variousphotolithographic masks are known to those skilled in the art. Theemitted light 35 passes from a light source 34 through the mask 58becoming masked or patterned light 37 and is concentrated throughoptical components 60 as a focused patterned light 61. The focusedpatterned light 61 is thus restricted or directed to regions 39corresponding to a pattern 62 controlled by the mask 58 and the optics60. The light 61 locally and instantaneously energizes a fluid 36passing beneath the focused patterned light 61. A more efficientpatterning may thus be obtained than through direct, unmasked scanningand narrowly targeted illumination of the workpiece surface as maskedregions of the workpiece may be illuminated, effecting excitation ofboth the fluid 36 and the layer 32.

As illustrated in FIGS. 3A-3E, block diagrams illustrating the steps ofproducing carbon based electronics construction configured according toone embodiment of the present invention. The method provides a carbonlayer 32. The carbon layer, may, in one embodiment be disposed upon asubstrate 30. The carbon layer 32 may comprise a layer of Diamond-likeCarbon, a Single Walled Nanotube mat, or a layer of graphene. Oneskilled in the art will readily appreciate that other carbon basedmolecules having sp2 or a combination or sp2 and sp3 bonding may beemployed in similar ways. In one such embodiment, a single wallednanotubes mat may be configured from at least one single wallednanotube, split along its longitudinal axis. What remains is a sheet ofsp2 bonded carbon with a thickness on the order of a few Angstroms,structurally analogous to graphene. Mats or layers of graphene, orDiamond-like carbon may be deposited using chemical vapor deposition orother known techniques. These mats or layers may, in accord with oneembodiment of the present invention, be aligned with a laser 34. In oneembodiment, this laser 34 is a stepper laser. In one embodiment of thepresent invention, the laser 34 may be configured with lenses andoptical components 60 and other components configured of or coated withmaterials resistant to chemical attack, including, but not limited tosapphire, diamond-like carbon or other suitably resistant coatings.Between the surface of the carbon wafer 32 and the chemically resistantlaser 34 a flow of fluid 36 is introduced. The fluid may be in eitherthe gaseous or liquid phases, or such other phases as are best suited toa particular doping agent. As illustrated in FIG. 4, alternativeembodiments where the doping agent is applied by spinning a layer ofcondensed phase doping agent or doping agent precursor 136 on thesurface of the carbon wafer 32. The fluid 36, 136 may comprise desireddoping agents or their precursors. Doping agents may be selected basedon the electrical characteristics of the doped carbon structure and onthe response of the doping agent or its precursors to photonic exposure.

Referring again to FIGS. 3A-3F, the carbon layer 32 is then selectivelyirradiated with laser light, illuminating only those areas of the layerwhere the circuit design requires doping 38, 40. Depending on the dopingagent used, the resulting doped regions 39 are may be either N-typeregions 40, P-type regions 38, highly electrically conductive regions50, or electrically insulative regions 42. As the light 61 passesthrough the fluid flow 136, 36, into the carbon layer 32, carbon tocarbon bonds are excited, facilitating bonding between the carbon layer32 and the doping agent 136, 36. The same light exposure effects adissociation of precursor molecules 136, 36, resulting in a release ofdoping agent radicals or other excited state molecules. Having excitedstate carbon bonds in close proximity to excited state doping agents ordoping agent radicals markedly increases adsorption in irradiated areas,while leaving non-irradiated areas substantially free of doping agents,that is with a level of doping agent inadequate to significantly effectthe electrical properties of the carbon.

Successive layers of carbon may be deposited and doped in this way,simply by depositing a second or subsequent layer of carbon 44,introducing a doping agent fluid 136, 36, and irradiating the fluid andcarbon layer 44. As the carbon irradiation and exposure to doping agentoccur at the surface of the carbon, layers disposed beneath the top mostlayer will be uneffected by the process. The building of successivelayers permits the construction of three dimensional circuits, such asthose illustrated in FIG. 3E and in FIG. 5. FIG. 3E illustrates oneembodiment of the present invention wherein horizontal 52 and vertical54 transistors are shown, as well as a MISFET (Metal InsulatorSemiconductor Field Effect Transistor) 56. The production of such acomponent may be conducted, in accordance with one embodiment of thepresent invention, in an enclosed environment using automated waferhandling tools. As no photoresist or associated cleaning and etchingsteps are required, the production of such devices may be carried out ina closed environment, minimizing wafer handling and any attendantcontamination. A similar process may be employed to prepare an inverter,a simple example of which is shown in FIG. 5.

Describing now in more detail, the three dimensional circuit configuredaccording to one embodiment of the present invention is illustrated inFIG. 3E. The doped wafer device 10 is formed of layers of single wallednanotube mats with selective areas of each successive mat doped tocreate N 40, P 38, and conductive regions 50. From the foregoingdescription, one skilled in the art will readily appreciate that insteadof single walled nanotube mats, other layers of sp2 and or sp3 bondedcarbon may be used, such as graphene. As is also well known in the art,the juxtaposition of doped N 40 and P 38 produces transistors. In oneembodiment of the present invention, such juxtaposition may be obtainedin a single layer, producing a “horizontal” transistor 52, or may beproduced by the superposition of alternating doped layers, producing a“vertical” transistor 54. Vias or conductive elements 50 may be formedwithin the structure to connect the transistors and link thesetransistors contacts with external components.

Contacts 64 for carbon based electrical components configured accordingto on embodiment of the present invention may be of indium or othersuitable material, and may be configured to provide for flip chipconfiguration or bump bonding. Examples of flip chips are well known tothose skilled in the art.

The foregoing description of the embodiments of the invention has beenpresented for the purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formdisclosed. Many modifications and variations are possible in light ofthis disclosure. It is intended that the scope of the invention belimited not by this detailed description, but rather by the claimsappended hereto.

1. A carbon based electrical component, said carbon based electricalcomponent comprising: A three dimensional carbon based electricalcircuit comprising a plurality of layers of carbon material; At leastone section of each layer in said plurality of layers being doped in atleast one layer doping pattern; Said at least one layer doping patternof each said layer being aligned to said at least one layer dopingpattern in an adjacent layer of said plurality of layers so as toproduce a desired vertical circuit.